This past year the focus of the research has been on the manner in which factors found at an inflammatory site may impact on the PGE2-cAMP dependent signal transduction pathway involved in MMP production by monocytes. The extracellular matrix component SPARC/osteonectin was shown to induce PGHS-2, eicosanoid and MMP production which was primarily attributed to a peptide (3.2) found in domain III of SPARC. SLPI, a prominent component of saliva, was shown to be a potent inhibitor of PGHS- 2 and MMP production by monocytes at concentrations of 0.1 to 10 microgram/ml, well within the physiological range of 1 to 20 microgram of SPARC/ml of saliva. In our studies on the role of cytokines in the regulation of PGHS-2 and MMP, TNFalpha was shown to enhance LPS-induced PGHS-2 and MMP production. When added to monocyte cultures alone, TNFalpha failed to induce PGHS-2 or interstitial collagenase but did increase the basal levels of gelatinase B, indicating differential regulation of this MMP. The role of tyrosine kinases in the regulation of the PGE2-cAMP dependent pathway leading to MMP production by monocytes are being evaluated. The tyrosine kinase inhibitor herbimycin A was shown to inhibit the induction of PGHS-2 and MMP. This inhibition occurred at an early step in the signal transduction process since PGE2 or Bt2cAMP restored PGHS-2 and MMP production in herbimycin A inhibited monocyte cultures. Phosphatases also play an important role in signal regulation. Addition of the phosphatase inhibitor okadaic acid resulted in a significant enhancement of LPS-induced PGHS-2 and MMP. The presence of these mediators in tissues from periodontal lesions are being evaluated by immunohistochemistry and in situ hybridization. Areas of connective tissue destruction contained large numbers of PGHS-2 positive macrophages as well as some positive fibroblasts and epithelial cells. Interstitial collagenase was localized to the macrophages, fibroblasts, and epithelial cells.